Multi-element bioresorbable intravascular stent

ABSTRACT

A multi-element, bioresorbable, vascular stent may be used to maintain or enhance patency of a blood vessel. The stent may be used in peripheral blood vessels, which may be long and/or tortuous. By using multiple, separate stent elements that are balloon expandable, the multi-element stent may be stronger than a traditional self-expanding stent but may also be more flexible, due to its multiple-element configuration, than a traditional balloon-expandable stent. Thus, the multi-element, bioresorbable, vascular stent described herein may be particularly advantageous for treating long lesions in tortuous peripheral blood vessels.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit and priority of U.S. ProvisionalPatent Application No. 62/127,370, entitled “MULTI-ELEMENT BIORESORBABLEINTRAVASCULAR STENT”, filed on Mar. 3, 2015, the full disclosure of theabove referenced application is incorporated herein by reference.

FIELD OF THE INVENTION

The present application pertains generally to the field of medicaldevices. More specifically, the present application pertains tobioresorbable vascular stents for tortuous vessels.

BACKGROUND

Atherosclerotic cardiovascular disease is the leading cause of death anddisability in the world, accounting for nearly one-third of all humanmortality. Over the past fifty years, significant progress has been madein the understanding and primary prevention of atherosclerosis. Still,as patients age and their arteries become brittle and elongated, earlyatherosclerotic plaques inexorably progress to their occlusive end-stageand induce the clinical syndromes of angina pectoris (chest pain),transient ischemic attack (reduced blood flow to the heart) andclaudication (leg pain due to poor circulation) and their sinisterend-stages of myocardial infarction (“heart attack”), stroke andamputation.

In the modern era, the mainstay of therapy for established vascularlesions is percutaneous balloon angioplasty (dilating the constrictedartery with a balloon catheter) and stent implantation. The procedure iswidely used, over 2,000,000 procedures performed annually, and theshort-term results are favorable in >95% of patients. Significantproblems with angioplasty and stenting remain, however, including therequirement for continued antiplatelet medication as the artery heals,the frequent need for early re-intervention for restenosis (when thestented artery closes down again), and thrombosis (clot formation).Furthermore, although there has been remarkable progress inintravascular stent development, stents still generate an alarmingnumber of long-term complications, including fracture and latethrombosis.

In order to circumvent the myriad problems associated with permanentmetal implants, stents that slowly dissolve after deployment have longbeen imagined and researched. Due to their temporary nature, suchdevices are also known as “scaffolds” rather than “stents” which remainin the body permanently. Bioresorbable vascular scaffolds (BVS or“bioresorbable stents”) potentially offer several key biologic andphysiologic advantages, including: (1) effective scaffolding without thepermanence of a metal implant; (2) attenuation of chronic inflammationand foreign body reaction; (3) promotion of adaptive vascularremodeling; (4) restoration of physiologic vasoactive function; and (5)facilitation of imaging and surveillance during follow-up. Despite theirpromise, however, the devices have proven challenging to successfullydesign, develop and manufacture. At the current time, only two coronarydevices and a single peripheral device are available commercially inEurope, and no devices have yet been approved for use in the UnitedStates.

A key limitation of intravascular stents is their inability to conformto and accommodate the natural bending and twisting of blood vesselsduring human movement. This is particularly problematic in the bloodvessels of the extremities, which bend and twist in unpredictablefashion, depending on the type, degree and rapidity of human motion. Forinstance, Cheng et al. quantified in vivo arterial deformation usingmagnetic resonance angiography and found that, during movement from thesupine to the fetal position, the superficial femoral artery (SFA)shortened an average of 13% and twisted an average of 60°. A subsequentstudy in elderly subjects found lesser degrees of shortening withflexion, but substantially more curvature and buckling. Other studieshave had similarly dramatic results.

The motion and deformation of stents implanted in actual human SFAs hasalso been studied. For instance, Nikanorov et al. deployed eleven 100 mmself-expanding nitinol stents in the femoropopliteal arteries of eightcadavers and assessed length and deflection via lateral view radiographsobtained during simulated flexion. The results showed that stentsimplanted in the SFA and popliteal arteries exhibited compression of upto 10.7%, depending on the degree of flexion. More notably, stentsimplanted in the mid-popliteal artery bent an average of 54° when theleg was fully flexed.

Stents implanted in short, motionless arteries are typically rigid andnon-deformable. So-called “balloon-expandable” stents are deployed byinflating their delivery balloon within the target lesion and embeddingthe rigid scaffold within the vessel wall. The final stent shape isfixed, casted and restrained by the contour of its surrounding vessel.Its architecture is permanent; reimaging the device over time generallyreveals no change in the diameter that was achieved during theprocedure.

In contrast, the length and motion of the long extremity vesselsmandates that stents designed for this anatomic location have theproperties of flexibility and conformability. Most devices designed forthe extremities are made of a nickel-titanium alloy known as “Nitinol”which has intrinsic properties of super-elasticity and shape memory.Nitinol stents are “self-expanding”, they are deployed by progressivelyreleasing the device from a long tube in which it is housed. Thedelivery system does not contain a balloon (although the device isroutinely “post-dilated” with a balloon that is separately inserted).Unlike balloon-expandable stents, self-expanding Nitinol stents areneither rigid nor fixed. Their flexibility allows them to the recoverwhen deformed, a critical property for a long device implanted into anextremity artery. In this respect, Nitinol stents resemble bypassgrafts: flexible, long conduits that carry blood past obstructivelesions.

However, the necessity for flexibility and conformability in peripheralvascular stents means that these stents have historically had far lessradial strength than typical balloon expandable stents. In this regard,such flexible, conformable stents do little to actually “stent” (or“prop open”) the artery; unconstrained by a scaffold, the artery is freeto collapse over time. Furthermore, stents designed in this manner mustbe “oversized,” to remain in place and continue to exert a “chronicoutward force” upon the vessel until such time that the nominal diameterof the device is reached. Some have theorized that the chronic forceimparts continuous injury to the artery, resulting in poor long-termpatency. Thus, the design of an effective, self-expanding, flexiblestent is fundamentally different from traditional, rigid,“balloon-expandable” metal stents, which exert a singular “stretch” atthe time of implantation and then remain inert as the vessel recoversand remodels.

The length and persistent motion of the extremity arteries also lead toa tendency toward fracture of stents implanted in those arteries. Stentfracture following femoropopliteal implantation is alarmingly common.Movement of the legs is a complex motion; loading of the hips and kneesduring ambulation repeatedly compresses the arteries axially and caneven produce multidimensional bends, twists and kinks. This results insingle or multiple strut fractures or, in severe cases, complete stenttransection. Fracture is more common after implantation of long and/oroverlapping stents and, possibly, in more active patients. Fracture ofintravascular stents is clearly associated with restenosis.

Therefore, it would be advantageous to have a bioresorbable stent foruse in peripheral vasculature that is easier to design, develop andmanufacture than currently available stents. Ideally, such a stent wouldhave a desirable flexibility and conformability profile while alsohaving sufficient strength to withstand the stresses placed onperipheral vascular stents, as described above. This would make thestent more useful and effective, and safe for the treatment of long,tortuous blood vessels. Ideally, such a stent would also provide atleast some of the advantages of absorbable (or “bioresorbable”) stentslisted above. At least some of these objectives will be met by theembodiments described below.

SUMMARY

The embodiments herein describe an apparatus for maintaining the luminalintegrity of long, naturally moveable and flexible human blood vesselsby simultaneous deployment of multiple independent, repeating, rigidscaffold units. The embodiments may include multiple, rigid, repeatingunits that are closely spaced within the vessel but do not touch oneanother, even when skeletal movement or myocardial contraction causesthe vessel to move.

In some embodiments, a stent may include multiple, rigid, potentiallyarticulating elements, which are simultaneously implanted along thelength of a vessel via balloon inflation. Each element of the stent mayhave relatively high radial force (rigidity), similar or greater inmagnitude to that of traditional, balloon-expandable stents. Eachelement may also be relatively short and rigid, so that its nominaldiameter will be reached immediately upon balloon inflation, and thus itwill not exert chronic forces upon the vessel. Additionally, becauseeach element is relatively short in length, each may move independently,in concert with the segment of artery into which it is implanted. Inthis way, such a stent may be used safely in any vessel of the body,regardless of the vessel's length, proximity to joints or range ofmotion. Finally, in some embodiments, all the elements of the stent maybe morphologically identical, so that their fabrication may be simplerthan that used for currently available stents.

In one aspect, a method of making a multi-element, bioresorbable,vascular stent may involve forming a length of the bioresorbable,vascular stent from a bioresorbable material that is balloon expandableand not self-expanding and cutting the length of the bioresorbable,vascular stent to form multiple stent elements of the stent. In someembodiments, forming the length of the bioresorbable, vascular stentcomprises using an additive manufacturing process. For example, theadditive manufacturing process may be micro-stereolithography. In someembodiments, the additive manufacturing process may be 3D printing. Invarious embodiments, the bioresorbable material may be poly(L-lacticacid) (PLLA), polyglycolic acid (PGA), or poly(iodinateddesaminotyrosyl-tyrosine ethyl ester) carbonate. Some embodiments mayfurther involve applying a coating to the bioresorbable material. Insome embodiments, the coating may be poly-D,L-lactide (PDLLA).Optionally, the method may further involve applying a drug to the stent.For example, the drug may be everolimus or any other anti-proliferativedrug, in various embodiments.

In another aspect, a device for placement within a blood vessel tomaintain or enhance blood flow through the blood vessel may includemultiple, balloon-expandable, bioresorbable, vascular stent elementsconfigured to be implanted in the blood vessel as a multi-element stent,with the multiple stent elements not touching one another. In someembodiments, the stent elements are fabricated by an additivemanufacturing process.

In some embodiments, stent elements comprise a first set of closed cellsand a second set of closed cells, wherein the first set of closed cellshave a different shape or size than the second set of closed cells. Thefirst set of closed cells may have a repeating longitudinally alignedpattern and a repeating circumferentially aligned pattern. The secondset of closed cells may also have a repeating longitudinally alignedpattern and a repeating circumferentially aligned pattern. The first setof closed cells and the second set of closed cells may becircumferentially offset and have a helically aligned alternatingpattern.

In an embodiment, the first set of closed cells are larger cells havinga first opening dimension and the second set of closed cells are smallercells having a second opening dimension smaller than the first openingdimension. Each of the larger closed cells may be formed by at least onewider strut between adjacent longitudinally aligned larger closed cellsand at least one thinner strut between adjacent circumferentiallyaligned larger closed cells. Larger closed cells may also be formed byat least one intermediate-width strut, wherein the intermediate-widthstrut between adjacent helically aligned larger closed cells and smallerclosed cells.

In another embodiment, the first set of closed cells have a firstlobular shape and the second set of closed cells have a second lobularshape. The first set of closed cells may comprise longitudinally alignedlobes and circumferentially aligned lobes. Longitudinally aligned lobesmay be larger than the circumferentially aligned lobes. Adjacentlongitudinally aligned lobes may be connected by longitudinal connectingstruts and adjacent circumferentially aligned lobes may be connected bycircumferential connecting struts.

In an embodiment, the first set of closed cells are ratcheting cellscomprising a longitudinally aligned ratcheting strut. Teeth on a portionof the ratcheting strut may be configured to move within a cavity whileexpanding the element and engage a pawl.

In an embodiment, the first set of closed cells are bistable cellscomprising a circumferentially aligned bistable strut having a bistablespring band configuration. The bistable struts may have a concavo-convexshape with the concave curve longitudinally oriented.

In an alternative embodiment, the stent elements may have a corrugatedcylindrical configuration with alternating convex ridges and concavegrooves. Corrugated elements may have solid walls or non-solid wallswith cell patterns.

In another embodiment, the stent elements comprise an alternatingsequence of two larger cells and a set of smaller cells, wherein the twolarger cells are formed by a pivoting strut between the two largercells. The pivoting strut may be configured to pivot from a less rigidstate to a more rigid state.

In another aspect, a method for maintaining or enhancing blood flowthrough a blood vessel may involve advancing a balloon catheter into theblood vessel, expanding a balloon on the balloon catheter to expandmultiple, bioresorbable, vascular stent elements mounted on the balloonto contact an inner wall of the blood vessel, deflating the balloon,while leaving the vascular stent elements in place in the blood vessel,and removing the balloon catheter from the blood vessel. In someembodiments, the blood vessel may be a peripheral blood vessel. In someembodiments, expanding the stent elements comprises expanding at leastfour elements. In some embodiments, the elements are separated from oneanother along the balloon, wherein expanding the elements comprisesdelivering the elements to the inner wall of the blood vessel in aspaced-apart configuration.

This and other aspects of the present disclosure are described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Present embodiments have other advantages and features which will bemore readily apparent from the following detailed description and theappended claims, when taken in conjunction with the accompanyingdrawings, in which:

FIGS. 1A-1C are side views of a self-expanding Nitinol stent placed in adistal SFA and popliteal artery, illustrated during different amounts ofleg flexion.

FIGS. 2A and 2B are side and magnified views, respectively, of afull-length bioresorbable vascular scaffold, according to oneembodiment.

FIGS. 3A and 3B are side and magnified views, respectively, of abioresorbable vascular scaffold designed with multiple, rigid,independent elements, according to one embodiment.

FIGS. 4A-4D are various views of the bioresorbable vascular scaffold ofFIGS. 3A and 3B illustrated in place along a curved tube to illustratethe ability of the stent elements to conform to curves in a bloodvessel, according to one embodiment.

FIGS. 5A-5C are side, end-on and magnified views, respectively, of astent, according to one embodiment.

FIGS. 6A and 6B are side and magnified views, respectively, of a stent,according to an alternative embodiment.

FIG. 7 is a schematic diagram of a micro-stereolithograph used to createa stent, according to one embodiment.

FIG. 8A is a two-dimensional depiction of an element having a lobularcell structure. FIG. 8B is a magnified view of the cells in FIG. 8A.FIG. 8C shows the stent element of FIG. 8A in cylindrical form.

FIG. 9A is a two-dimensional depiction of an element having analternative lobular cell structure. FIG. 9B is a magnified view of acell in FIG. 9A.

FIG. 10A is a two-dimensional depiction of an element having aratcheting configuration. FIG. 10B is a magnified view of the cells inFIG. 10A. FIG. 10C is an isometric view of the cells in FIG. 10A. FIG.10D is a cross-sectional view of the cells in FIG. 10C showing aratchet. FIG. 10E is a magnified view of a ratchet in FIG. 10D. FIG. 10Fis an alternative view of a ratchet in cross-section.

FIG. 11A is a two-dimensional depiction of an element having a bistablespring band configuration. FIG. 11B is a magnified view of the cells inFIG. 11A. FIG. 11C is an isometric view of the cells in FIG. 11A. FIG.11D is a cross-sectional view of the cells in FIG. 11C showing thecurvature of bistable strut 1103. FIG. 11E is a magnified view of abistable strut 1103 in FIG. 11D. FIG. 11F is an alternative view of abistable strut 1103 in cross-section.

FIG. 12A is a two-dimensional depiction of an element having a pivotingconfiguration. FIG. 12B is a magnified view of the cells in FIG. 12A.

FIG. 13A is a side view of a cylindrical element having a corrugated orarch configuration. FIG. 13B is a top view of a corrugated element. FIG.13C is a magnified view of the element in FIG. 13B. FIG. 13D is anisometric view of a cylindrical element having a corrugatedconfiguration. FIG. 13F a magnified view of the element in FIG. 13E.

DETAILED DESCRIPTION

While the invention has been disclosed with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the invention. In addition, manymodifications may be made to adapt to a particular situation or materialto the teachings of the invention without departing from its scope.

Throughout the specification and claims, the following terms take themeanings explicitly associated herein unless the context clearlydictates otherwise. The meaning of “a”, “an”, and “the” include pluralreferences. The meaning of “in” includes “in” and “on.” Referring to thedrawings, like numbers indicate like parts throughout the views.Additionally, a reference to the singular includes a reference to theplural unless otherwise stated or inconsistent with the disclosureherein.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any implementation described herein as“exemplary” is not necessarily to be construed as advantageous overother implementations.

Various embodiments are described herein with reference to the figures.The figures are not drawn to scale and are only intended to facilitatethe description of the embodiments. They are not intended as anexhaustive description of the invention or as a limitation on the scopeof the invention. In addition, an illustrated embodiment needs not haveall the aspects or advantages shown. An aspect or an advantage describedin conjunction with a particular embodiment is not necessarily limitedto that embodiment and can be practiced in any other embodiments even ifnot so illustrated.

FIGS. 1A-1C are side views of a self-expanding, Nitinol stent 200 placedin a distal SFA and popliteal artery A, illustrated during differentamounts of leg flexion. FIG. 1A illustrates stent 200 with the leg inthe neutral position, minimal flexion/mostly extended. FIG. 1Billustrates stent 200 during partial flexion, with a circle and bendradius 202 illustrating the angle of flexion and the curved deformationof stent 200. FIG. 1C illustrates stent 200 during greater flexion. AsFIGS. 1A-1C illustrate, stent 200 is markedly deformed by flexion of theleg.

Referring now to FIG. 7, in one embodiment, bioresorbable vascularscaffolds (BVSs) may be manufactured using a micro-stereolithographysystem 100 (or “3D printing system”). Several examples of currentlyavailable systems that might be used in various embodiments include, butare not limited to: MakiBox A6, Makible Limited, Hong Kong; CubeX, 3DSystems, Inc., Circle Rock Hill, S.C.; and 3D-Bioplotter, (EnvisionTECGmbH, Gladbeck, Germany).

The micro-stereolithography system may include an illuminator, a dynamicpattern generator, an image-former and a Z-stage. The illuminator mayinclude a light source, a filter, an electric shutter, a collimatinglens and a reflecting mirror that projects a uniformly intense light ona digital mirror device (DMD), which generates a dynamic mask. FIG. 7shows some of these components of one embodiment of themicro-stereolithography system 100, including a DMD board, Z-stage,lamp, platform, resin vat and an objective lens. The details of 3Dprinting/micro-stereolithography systems and other additivemanufacturing systems will not be described here, since they are wellknown in the art. However, according to various embodiments, anyadditive manufacturing system or process, whether currently known orhereafter developed, may potentially be used to fabricate BVSs withinthe scope of the present invention. In other words, the scope of theinvention is not limited to any particular additive manufacturing systemor process.

In one embodiment, the system 100 may be configured to fabricate BVSsusing dynamic mask projection micro-stereolithography. In oneembodiment, the fabrication method may include first producing 3Dmicrostructural scaffolds by slicing a 3D model with a computer programand solidifying and stacking images layer by layer in the system. In oneembodiment, the reflecting mirror of the system is used to project auniformly intense light on the DMD, which generates a dynamic mask. Thedynamic pattern generator creates an image of the sliced section of thefabrication model by producing a black-and-white region similar to themask. Finally, to stack the images, a resolution Z-stage moves up anddown to refresh the resin surface for the next curing. The Z-stage buildsubsystem, in one embodiment, has a resolution of about 100 nm andincludes a platform for attaching a substrate, a vat for containing thepolymer liquid solution, and a hot plate for controlling the temperatureof the solution. The Z-stage makes a new solution surface with thedesired layer thickness by moving downward deeply, moving upward to thepredetermined position, and then waiting for a certain time for thesolution to be evenly distributed.

In any of the described embodiments, stents or stent elements may bemanufactured as a sheet and wrapped into cylindrical form.Alternatively, stents or stent elements may be manufactured incylindrical form using an additive manufacturing process.

In an embodiment shown in FIGS. 6A-6B, stents or stent elements may befabricated using non-bioresorbable material, including 1,6-hexanedioldiacrylate with 2% DMPA as a photoinitiator, and 0.10% Tinuvin 327 as alight absorber. In various alternative embodiments, the stent or stentelement may be made from any suitable bioresorbable material, such asbut not limited to poly(L-lactic acid) (PLLA), polyglycolic acid (PGA),poly(iodinated desaminotyrosyl-tyrosine ethyl ester) carbonate, or thelike.

In alternative embodiments, any suitable polymer may be used toconstruct the stent. The term “polymer” is intended to include a productof a polymerization reaction inclusive of homopolymers, copolymers,terpolymers, etc., whether natural or synthetic, including random,alternating, block, graft, branched, cross-linked, blends, compositionsof blends and variations thereof. The polymer may be in true solution,saturated, or suspended as particles or supersaturated in the beneficialagent. The polymer can be biocompatible, or biodegradable. For purposeof illustration and not limitation, the polymeric material may include,but is not limited to, phosphorylcholine, polycaprolactone,poly-D,L-lactic acid, poly-L-lactic acid, poly(lactideco-glycolide),poly(hydroxybutyrate), poly(hydroxybutyrate-co-valerate), polydioxanone,polyorthoester, polyanhydride, poly(glycolic acid), poly(glycolicacid-co-trimethylene carbonate), polyphosphoester, polyphosphoesterurethane, poly(amino acids), cyanoacrylates, poly(trimethylenecarbonate), poly(iminocarbonate), polyalkylene oxalates,polyphosphazenes, polyiminocarbonates, and aliphatic polycarbonates,fibrin, fibrinogen, cellulose, starch, collagen, polyurethane includingpolycarbonate urethanes, polyethylene, polyethylene terapthalate,ethylene vinyl acetate, ethylene vinyl alcohol, silicone includingpolysiloxanes and substituted polysiloxanes, polyethylene oxide,polybutylene terepthalate-co-PEG, PCL-co-PEG, PLA-co PEG, polyacrylates,polyvinyl pyrrolidone, polyacrylamide, and combinations thereof.Non-limiting examples of other suitable polymers include thermoplasticelastomers in general, polyolefin elastomers, EPDM rubbers and polyamideelastomers, and biostable plastic material including acrylic polymers,and its derivatives, nylon, polyesters and expoxies. In someembodiments, the stent may include one or more coatings, with materialslike poly-D,L lactide (PDLLA). Additionally, some stents may include acoating with materials like the antiproliferative drug everolimus. Thesematerials are merely examples, however, and should not be seen aslimiting the scope of the invention.

Some or all of the stent may comprise closed-cell structures formed byintersecting struts. Closed-cell structures may comprise diamond,square, rectangular, parallelogrammatic, triangular, pentagonal,hexagonal, heptagonal, octagonal, clover, lobular, circular, elliptical,and/or ovoid geometries. Closed-cells may also comprise slotted shapessuch as H-shaped slots, I-shaped slots, J-shaped slots, and the like.Additionally or alternatively, stent may comprise open cell structuressuch as spiral structures, serpentine structures, zigzags structures,etc. Strut intersections may form pointed, perpendicular, rounded,bullnosed, flat, beveled, and/or chamfered cell corners. In anembodiment, stent may comprise multiple different cells having differentcell shapes, orientations, and/or sizes.

In general, the embodiments described herein are multi-element,bioresorbable, vascular stents (or “vascular scaffolds”). These stentsincluded multiple stent sections, or “elements,” which are separate fromone another but may be referred to together as a multi-element stent.Generally, the stent elements of the multi-element stents describedherein will be sufficiently rigid to provide a desired level of strengthto withstand the stresses of the vessel in which they are placed, suchas a tortuous peripheral vessel. At the same time, a multi element stentwill also be flexible, due to the fact that it is made up of multipleseparate elements, thus allowing for placement within a curved,torturous blood vessel. Additionally, the multi element stents describedherein will usually be balloon-expandable rather than self-expanding,since balloon-expandable stents are typically stronger thanself-expanding stents. Each balloon expandable polymeric element of thestent may have relatively high radial force (rigidity) due to thedescribed structures. Elements may have a radial strength significantlyhigher than self-expanding stents that is similar or greater inmagnitude to that of traditional, metal balloon-expandable stents, suchas those made of steel or cobalt-chromium.

FIGS. 3A, 3B and 4A-4D illustrate one embodiment of a multi-elementstent, as described herein. FIGS. 2A, 2B, 5A-5C, 6A and 6B illustratelonger stent segments. These longer stent segments are provided forexemplary purposes. In some embodiments, a longer stent segment, such asthose shown in FIGS. 2A, 2B, 5A-5C, 6A and 6B, may be formed during themanufacturing process and then cut into smaller stent segments/elementsto provide a multi-element stent. In other embodiments, a multi-elementstent may be made of multiple, longer stent segments, such as thoseshown in these figures.

As illustrated in FIGS. 2A-6B, in one embodiment, an intravascular stentmay include a closed-cell repeating diamond pattern. In alternativeembodiments, any other suitable stent pattern may be used. In thisembodiment, the stent may have a strut thickness of about 300-400 μm,although the system can potentially fabricate stents with struts as thinas about 50 μm (current coronary BVSs have a strut thickness of about158 μm).

As illustrated in FIGS. 5A-5C, in one embodiment, the stent 10 may havea length of about 22.53 mm, an outer diameter of about 3 mm, an innerdiameter of about 2.6 mm, and a wall thickness of about 0.2 mm. Thesemeasurements are provided only for exemplary purposes, however. Inalternative embodiments, the stent may have any suitable length,diameters and wall thickness. As illustrated in FIG. 5, in oneembodiment, the stent may have a diamond or other closed-cell pattern.In this embodiment, the stent comprises intermixed large and smallcells. Large cells may be aligned in the longitudinal and/or thecircumferential directions in a repeating pattern. Similarly, smallcells may be aligned in the longitudinal and/or the circumferentialdirections in a repeating pattern. Additionally or alternatively, smalland large cells may be helically aligned in an alternating pattern. Inan embodiment, small cells and large cells are circumferentially offset.Additionally, small cells may be formed at a central location betweenfour adjacent large cells. In an embodiment illustrated in FIG. 5, afirst opening dimension (1) of a large closed cell is about 0.68 mm, asecond opening dimension (2) of an adjacent small closed cell is about0.39 mm, a third dimension (3) of a width of a strut between twoup-to-down corners of the longitudinally aligned large closed cells isabout 0.25 mm, a fourth dimension (4) of a width of a strut between twostraight portions of the helically aligned large closed cell and smallclosed cell is about 0.2 mm, and a fifth dimension (5) of a width of astrut between two side-to-side corners of the circumferentially alignedlarge closed cells is about 0.12 mm. Again, these measurements areprovided for exemplary purposes only and are not intended to limit thescope of the invention.

In some embodiments, at least one wider strut extends between multiplecells to form a spiral along a length of the stent elements to enhancethe radial strength of each of the stent elements. In some embodiments,the wider strut extends from one end to an opposite end of one of thestent elements. In other embodiments, the wider strut does not extendfrom one end to an opposite end of one of the stent elements.

FIGS. 6A and 6B are side and magnified views, respectively, of the stent10, taken via a microscope. The illustrated dimensions are inmicrometers and again are provided only as examples.

Referring now to FIGS. 3A-4D, in one embodiment, a multi-element,bioresorbable, vascular stent 20 (or “multi-stent system”) may includemultiple stent elements 22, which in some embodiments may be formed bycutting a longer stent piece, such as that shown in FIGS. 2A, 2B, 5A-5C,6A and 6B, to form the multiple elements 22. In an embodiment, multiplestent elements 22 comprise cells having the same cell shapes,orientations, and/or sizes. In another embodiment, multiple stentelements 22 comprise cells having different cell shapes, orientations,and/or sizes. Stent 20 and individual stent elements 22 may have a highradial strength such that stent 20 and individual stent elements 22 areradially rigid and do not exert chronic outward force upon the vessel.Stent 20 and/or individual stent elements 22 may also be flexible alongthe longitudinal axis of the stent 20. The stent elements 22 aretypically placed in a blood vessel with a certain distance between eachadjacent stent element 22. The multi-element stent 20 may be fabricatedon and/or housed on a dowel or other support device. The multi-elementstent 20 may be used, for example, to treat long lesions in a bloodvessel. In some embodiments, the number of stent elements 22 in themulti-element stent 20 may be selected by a physician user depending ona length of a vascular lesion. In the embodiment shown in FIGS. 3A and3B, the multi-element stent 20 includes 14 stents, with an interval ofabout 1 mm between adjacent stent elements 22. The total length of themulti-element stent 20 is about 66 mm, and a single stent element 22 hasa length of about 3.07 mm, inner diameter of about 2.6 mm and outerdiameter of about 3 mm. Again, these dimensions are only one example,and any other suitable dimensions may be used in alternativeembodiments.

Referring now to FIGS. 4A-4D, in some embodiments, the stent elements 22of the multi-element stent 20 may be designed to accommodate a bendaround a corner, as illustrated. Some stent elements 22 remain in theirstraight, unbent configuration, while others conform to a bend. In analternative embodiment, one stent may be designed to bend around acorner.

FIGS. 8A-8C illustrate an embodiment of a stent element having a cloveror lobular cell configuration. While FIGS. 8A-8C depict cells with fourlobes, cells may have any number of lobes. FIG. 8A is a two-dimensionaldepiction of an element having a lobular cell structure. FIG. 8B is amagnified view of the cells in FIG. 8A. FIG. 8C shows the stent elementof FIG. 8A in cylindrical form wherein the two dimensional cells of FIG.8A are wrapped from left to right to form a cylinder. In thisembodiment, element 800 comprises intermixed lobular closed cells 801,802. Lobular cells 801 may be aligned in the longitudinal and/or thecircumferential directions in a repeating pattern. Similarly, lobularcells 802 may be aligned in the longitudinal and/or the circumferentialdirections in a repeating pattern. Additionally or alternatively,lobular cells 802 and lobular cells 801 may be helically aligned in analternating pattern. In an embodiment, lobular cells 802 and lobularcells 801 are circumferentially offset. Additionally, lobular cells 802may be formed at a central location between four adjacent lobular cells801. In an embodiment illustrated in FIGS. 8A-8C, longitudinal lobes 803aligned longitudinally are larger than circumferential lobes 804 alignedcircumferentially. Alternatively, longitudinal lobes 803 may be the samesize as circumferential lobes 804. Longitudinal lobes 803 of adjacentlongitudinally aligned lobular cells 801 may be connected bylongitudinal connecting struts 805. Circumferential lobes 804 ofadjacent circumferentially aligned lobular cells 801 may be connected bycircumferential connecting struts 806. In an embodiment, longitudinalconnecting struts 805 are wider than circumferential connecting struts806. Alternatively, longitudinal connecting struts 805 may have the samewidths as circumferential connecting struts 806. Element 800 may take acrimped form when mounted on an unexpanded balloon. Likewise, element800 may take an expanded form when expanded by a balloon. Concavities807 move away from the center of lobular element 800 as the lobular cell801 moves from a crimped state to an expanded state.

FIGS. 9A-9B illustrate an alternative embodiment of a stent elementhaving a clover or lobular cell configuration. While FIGS. 9A-9B depictcells with four lobes, cells may have any number of lobes. FIG. 9A is atwo-dimensional depiction of an element having this lobular cellstructure. FIG. 9B is a magnified view of a cell in FIG. 9A. A stentelement with the cell structure of FIG. 9A would have a wrap orientationof left to right to form a cylinder. In this embodiment, element 900comprises intermixed lobular closed cells 901, 902. Lobular cells 901may be aligned in the longitudinal and/or the circumferential directionsin a repeating pattern. Similarly, lobular cells 902 may be aligned inthe longitudinal and/or the circumferential directions in a repeatingpattern. Additionally or alternatively, lobular cells 902 and lobularcells 901 may be helically aligned in an alternating pattern. In anembodiment, lobular cells 902 and lobular cells 901 arecircumferentially offset. Additionally, lobular cells 902 may be formedat a central location between four adjacent lobular cells 901. In anembodiment, longitudinal lobes 903 aligned longitudinally may be largerthan circumferential lobes 904 aligned circumferentially. Alternatively,longitudinal lobes 903 may be the same size as circumferential lobes904. Longitudinal lobes 903 of adjacent longitudinally aligned lobularcells 901 may be connected by longitudinal connecting struts 905.Circumferential lobes 904 of adjacent circumferentially aligned lobularcells 901 may be connected by circumferential connecting struts 906. Inan embodiment, longitudinal connecting struts 905 are wider thancircumferential connecting struts 906. Alternatively, longitudinalconnecting struts 905 may have the same widths as circumferentialconnecting struts 906. Element 900 may take a crimped form when mountedon an unexpanded balloon. Likewise, element 900 may take an expandedform when expanded by a balloon. Concavities 907 move away from thecenter of lobular cell 901 as the lobular element 900 moves from acrimped state to an expanded state.

FIGS. 10A-10F illustrate an embodiment of a stent element having aratcheting configuration. While FIGS. 10A-10F depict cells with diamondconfigurations, cells may have any closed cell configuration. FIG. 10Ais a two-dimensional depiction of an element having a ratchetingconfiguration. FIG. 10B is a magnified view of the cells in FIG. 10A.FIG. 10C is an isometric view of the cells in FIG. 10A. FIG. 10D is across-sectional view of the cells in FIG. 10C showing the ratchet 1007.FIG. 10E is a magnified view of a ratchet 1007 in FIG. 10D. FIG. 10F isan alternative view of a ratchet 1007 in cross-section. A stent elementwith the cell structure of FIG. 10A would have a wrap orientation ofleft to right to form a cylinder. In this embodiment, element 1000comprises intermixed ratcheting cells 1001 and non-ratcheting cells1002. Ratcheting cells 1001 may be aligned in the longitudinal and/orthe circumferential directions in a repeating pattern. Similarly,non-ratcheting cells 1002 may be aligned in the longitudinal and/or thecircumferential directions in a repeating pattern. Additionally oralternatively, non-ratcheting cells 1002 and ratcheting cells 1001 maybe helically aligned in an alternating pattern. In an embodiment,non-ratcheting 1002 and ratcheting cells 1001 are circumferentiallyoffset. Additionally, non-ratcheting cells 1002 may be formed at acentral location between four adjacent ratcheting cells 1001. In anembodiment illustrated in FIGS. 10A-10F, ratcheting cells 1001 may havethe same or similar size as non-ratcheting cells 1002. Alternatively,ratcheting cells 1001 may be larger or smaller than non-ratcheting cells1002. Adjacent longitudinally aligned ratcheting cells 1001 may beconnected by longitudinal connecting struts 1005. Adjacentcircumferentially aligned ratcheting cells 1001 may be connected bycircumferential connecting struts 1006. In an embodiment, longitudinalconnecting struts 1005 may have larger lengths or widths thancircumferential connecting struts 1006. Alternatively, longitudinalconnecting struts 1005 may have the same lengths or widths ascircumferential connecting struts 1006. Ratcheting cells 1001 compriselongitudinally aligned ratcheting struts 1003. Longitudinally alignedcorners of ratcheting cells 1001 and/or longitudinal connecting struts1005 may comprise cavities 1008 to house linear racks 1009 on ratchetingstruts 1003. Pawl 1010 engages teeth 1011 of linear rack 1009. Element1000 may take a crimped form when mounted on an unexpanded balloon.Likewise, element 1000 may take an expanded form when expanded by aballoon. Linear rack 1007 moves in a longitudinal direction into cavity1008 (depicted as down to up in FIG. 10E and right to left in FIG. 10F)as the ratcheting element 1000 moves from a crimped state to an expandedstate. Ratchet 1007 would thereby increase the radial strength ofelement 1000.

FIGS. 11A-11F illustrate an embodiment of a stent element having abistable spring band configuration. While FIGS. 11A-11F depict cellswith diamond configurations, cells may have any closed cellconfiguration. FIG. 11A is a two-dimensional depiction of an elementhaving a bistable spring band configuration. FIG. 11B is a magnifiedview of the cells in FIG. 11A. FIG. 11C is an isometric view of thecells in FIG. 11A. FIG. 11D is a cross-sectional view of the cells inFIG. 11C showing the curvature of bistable strut 1103. FIG. 11E is amagnified view of a bistable strut 1103 in FIG. 11D. FIG. 11F is analternative view of a bistable strut 1103 in cross-section. A stentelement with the cell structure of FIG. 11A would have a wraporientation of left to right to form a cylinder. In this embodiment,element 1100 comprises intermixed bistable cells 1101 and non-bistablecells 1102. Bistable cells 1101 may be aligned in the longitudinaland/or the circumferential directions in a repeating pattern. Similarly,non-bistable cells 1102 may be aligned in the longitudinal and/or thecircumferential directions in a repeating pattern. Additionally oralternatively, non-bistable cells 1102 and bistable cells 1101 may behelically aligned in an alternating pattern. In an embodiment,non-bistable 1102 and bistable cells 1101 are circumferentially offset.Additionally, non-bistable cells 1102 may be formed at a centrallocation between four adjacent bistable cells 1101. In an embodimentillustrated in FIGS. 11A-11F, bistable cells 1101 may have the same orsimilar size as non-bistable cells 1102. Alternatively, bistable cells1101 may be larger or smaller than non-bistable cells 1102. Adjacentlongitudinally aligned bistable cells 1101 may be connected bylongitudinal connecting struts 1105. Adjacent circumferentially alignedbistable cells 1101 may be connected by circumferential connectingstruts 1106. In an embodiment, longitudinal connecting struts 1105 mayhave larger lengths or widths than circumferential connecting struts1106. Alternatively, longitudinal connecting struts 1105 may have thesame lengths or widths as circumferential connecting struts 1106.Bistable cells 1101 comprise circumferentially aligned bistable struts1103. Bistable struts 1103 have a bistable spring band configuration. Inan embodiment, bistable struts 1103 have a concavo-convex shape.Bistable struts 1103 may take a straight form or a bent form wherein thebistable strut 1103 bends in the concave direction. Rigidity of thebistable strut 1103 in the straight form increases radial strength ofthe element 1100. As depicted in FIGS. 11C-11F, the concave curve ofbistable strut 1103 is oriented in the longitudinal direction and wouldface a proximal or distal opening of the cylindrical element 1100.Element 1100 may take a crimped form when mounted on an unexpandedballoon. Likewise, element 1100 may take an expanded form when expandedby a balloon. Bistable strut 1103 would have a bent configuration in thecrimped form. In the expanded state, the bistable strut would have astraight configuration.

FIGS. 12A-12B illustrate an embodiment of a stent element having apivoting configuration. FIG. 12A is a two-dimensional depiction of anelement having a pivoting configuration. FIG. 12B is a magnified view ofthe cells in FIG. 12A. A stent element with the cell structure of FIG.12A would have a wrap orientation of left to right to form a cylinder.In this embodiment, element 1200 comprises an alternating sequence of 2larger cells 1201 and a set of smaller cells 1202. The two larger cells1201 allow bending of the free moving pivoting strut 1203 separating thetwo larger cells 1201. Element 1200 may take a crimped form when mountedon an unexpanded balloon. Likewise, element 1200 may take an expandedform when expanded by a balloon. FIGS. 12A-12B depict the pivoting strut1203 in an unstable, less rigid configuration present when the element1200 is in a crimped state. When expanded, the apex 1204 of the pivotingstrut 1203 would shift from the right to the left (based on theorientation in FIG. 12A-12B), thereby increasing the rigidity of thepivoting strut 1203 and increasing the radial strength of the element1200.

FIGS. 13A-13F illustrate an embodiment of a stent element having acorrugated or arch configuration. FIG. 13A is a side view of acylindrical element having a corrugated configuration. FIG. 13B is a topview of a corrugated element. FIG. 13C is a magnified view of theelement in FIG. 13B. FIG. 13D is an isometric view of a cylindricalelement having a corrugated configuration. FIG. 13F a magnified view ofthe element in FIG. 13E. Element 1300 comprises alternating convexridges 1301 and concave grooves 1302. In an embodiment, as depicted inFIGS. 13A, 13D, and 13E, element 1300 may comprise solid walls. In anembodiment, corrugated element 1300 may have a longitudinal length ofapproximately 3 mm. Alternatively, corrugated elements may havelongitudinal lengths of 1-2 mm. Short longitudinal lengths allow stentelements 1300 to be placed with solid walls. In another embodiment,corrugated element 1300 may have cell patterns cut into the corrugatedcylinder. Alternatively, element 1300 may be manufactured with arches,ridges, and cell patterns using an additive manufacturing process.Element 1300 may take a crimped form when mounted on an unexpandedballoon. Likewise, element 1300 may take an expanded form when expandedby a balloon. As the corrugated cell 1300 moves from a crimped state toan expanded state, ridges 1301 and/or valleys 1302 will widen.

Any suitable therapeutic agent (or “drug”) may be incorporated into,coated on, or otherwise attached to the stent, in various embodiments.Examples of such therapeutic agents include, but are not limited to,anti-thrombotics, anticoagulants, antiplatelet agents, anti-lipidagents, thrombolytics, anti-proliferatives, anti-inflammatories, agentsthat inhibit hyperplasia, smooth muscle cell inhibitors, antibiotics,growth factor inhibitors, cell adhesion inhibitors, cell adhesionpromoters, anti-mitotics, anti-fibrins, antioxidants, anti-neoplastics,agents that promote endothelial cell recovery, matrix metalloproteinaseinhibitors, anti-metabolites, anti-allergic substances, viral vectors,nucleic acids, monoclonal antibodies, inhibitors of tyrosine kinaseantisense compounds, oligio-nucleotides, cell permeation enhancers,hypoglycemic agents, hypolipidemic agents, proteins, nucleic acids,agents useful for erythropoiesis stimulation, angiogenesis agents,anti-ulcer/anti-reflux agents, and anti-nauseants/anti-emetics, PPARalpha agonists, sodium heparin, LMW heparins, heparoids, hirudin,argatroban, forskolin, vapriprost, prostacyclin and prostacylinanalogues, dextran, D-phe-pro-arg-chloromethylketone (syntheticanti-thrombin), glycoprotein IIb/IIIa (platelet membrane receptorantagonist antibody), recombinant hirudin, thrombin inhibitors,indomethacin, phenyl salicylate, beta-estradiol, vinblastine, ABT-627(astrasentan), testosterone, progesterone, paclitaxel, methotrexate,fotemusine, RPR-101511A, cyclosporine A, vincristine, carvediol,vindesine, dipyridamole, methotrexate, folic acid, thrombospondinmimetics, estradiol, dexamethasone, metrizamide, iopamidol, iohexol,iopromide, iobitridol, iomeprol, iopentol, ioversol, ioxilan, iodixanol,and iotrolan.

Examples of anti-thrombotics, anticoagulants, antiplatelet agents, andthrombolytics include, but are not limited to, sodium heparin, lowmolecular weight heparins, heparinoids, hirudin, argatroban, forskolin,vapriprost, prostacyclin and prostacylin analogues, dextran,Dphe-pro-arg-chloromethylketone (synthetic anti-thrombin), dipyridamole,glycoprotein IIb/IIIa (platelet membrane receptor antagonist antibody),recombinant hirudin, thrombin inhibitors, and thrombolytic agents.

Examples of cytostatic or anti-proliferative agents include, but are notlimited to, rapamycin and its analogs, including everolimus,zotarolimus, tacrolimus and pimecrolimus, angiopeptin, angiotensinconverting enzyme inhibitors, such as captopril, cilazapril orlisinopril, calcium channel blockers, such as nifedipine, amlodipine,cilnidipine, lercanidipine, benidipine, trifluperazine, diltiazem andverapamil, fibroblast growth factor antagonists, fish oil (omega 3-fattyacid), histamine antagonists, lovastatin, topoisomerase inhibitors, suchas etoposide and topotecan, as well as antiestrogens such as tamoxifen.

Examples of anti-inflammatory agents include, but are not limited to,colchicine and glucocorticoids, such as betamethasone, cortisone,dexamethasone, budesonide, prednisolone, methylprednisolone andhydrocortisone. Non-steroidal anti-inflammatory agents include, but arenot limited to, flurbiprofen, ibuprofen, ketoprofen, fenoprofen,naproxen, diclofenac, diflunisal, acetominophen, indomethacin, sulindac,etodolac, diclofenac, ketorolac, meclofenamic acid, piroxicam andphenylbutazone.

Examples of anti-neoplastic agents include, but are not limited to,alkylating agents including altretamine, bendamucine, carboplatin,carmustine, cisplatin, cyclophosphamide, fotemustine, ifosfamide,lomustine, nimustine, prednimustine, and treosulfin, antimitotics,including vincristine, vinblastine, paclitaxel, docetaxel,antimetabolites including methotrexate, mercaptopurine, pentostatin,trimetrexate, gemcitabine, azathioprine, and fluorouracil, andantibiotics, such as doxorubicin hydrochloride and mitomycin.Antiallergic agents include, but are not limited to, permirolastpotassium nitroprusside, phosphodiesterase inhibitors, prostaglandininhibitors, suramin, serotonin blockers, steroids, thioproteaseinhibitors, triazolopyrimidine, and nitric oxide.

Although particular embodiments have been shown and described, they arenot intended to limit the invention. Various changes and modificationsmay be made to any of the embodiments, without departing from the spiritand scope of the invention. The invention is intended to coveralternatives, modifications, and equivalents.

1. A device for placement within a blood vessel to maintain or enhanceblood flow through the blood vessel, the device comprising multiple,balloon-expandable, bioresorbable, vascular stent elements configured tobe implanted in the blood vessel as a multi-element stent, with themultiple stent elements not touching one another; wherein the stentelements comprise a first set of closed cells and a second set of closedcells, wherein the first set of closed cells have a different shape orsize than the second set of closed cells; wherein the first set ofclosed cells have a repeating longitudinally aligned pattern and arepeating circumferentially aligned pattern, wherein the second set ofclosed cells have a repeating longitudinally aligned pattern and arepeating circumferentially aligned pattern, wherein the first set ofclosed cells and the second set of closed cells are circumferentiallyoffset, and wherein the first set of closed cells and the second set ofclosed cells have a helically aligned alternating pattern.
 2. The deviceof claim 1, wherein the first set of closed cells are larger cellshaving a first opening dimension and the second set of closed cells aresmaller cells having a second opening dimension smaller than the firstopening dimension; wherein each of the larger closed cells is formed byat least one wider strut and at least one thinner strut, wherein thewider strut has a first width and the thinner strut has a second widthless than the first width; and wherein the wider struts are betweenadjacent longitudinally aligned larger closed cells, and wherein thethinner struts are between adjacent circumferentially aligned largerclosed cells.
 3. The device of claim 2, wherein each of the largerclosed cells is further formed by at least one intermediate-width strut,wherein the intermediate-width strut has a third width smaller than thefirst width and larger than the second width; and wherein theintermediate-width struts are between adjacent helically aligned largerclosed cells and smaller closed cells.
 4. The device of claim 1, whereinfirst set of closed cells have a first lobular shape and the second setof closed cells have a second lobular shape.
 5. The device of claim 4,wherein each of the cells of the first set of closed cells compriselongitudinally aligned lobes and circumferentially aligned lobes;wherein the longitudinally aligned lobes are larger than thecircumferentially aligned lobes.
 6. The device of claim 5, whereinadjacent longitudinally aligned lobes are connected by longitudinalconnecting struts and adjacent circumferentially aligned lobes areconnected by circumferential connecting struts.
 7. The device of claim1, wherein the first set of closed cells are ratcheting cells and thesecond set of closed cells are non-ratcheting cells.
 8. The device ofclaim 7, wherein each of the ratcheting cells comprise a longitudinallyaligned ratcheting strut; wherein teeth on a portion of the ratchetingstrut are configured to move within a cavity and engage a pawl.
 9. Thedevice of claim 1, wherein the first set of closed cells are bistablecells and the second set of closed cells are non-bistable cells, whereinthe bistable cells comprise a circumferentially aligned bistable struthaving a bistable spring band configuration.
 10. The device of claim 9,wherein the bistable struts have a concavo-convex shape with the concavecurve longitudinally oriented.
 11. A device for placement within a bloodvessel to maintain or enhance blood flow through the blood vessel, thedevice comprising multiple, balloon-expandable, bioresorbable, vascularstent elements configured to be implanted in the blood vessel as amulti-element stent, with the multiple stent elements not touching oneanother; wherein the stent elements have a corrugated cylindricalconfiguration with alternating convex ridges and concave grooves. 12.The device of claim 11, wherein the stent elements have solid walls. 13.The device of claim 11, wherein the stent elements have non-solid wallswith cell patterns.
 14. A device for placement within a blood vessel tomaintain or enhance blood flow through the blood vessel, the devicecomprising multiple, balloon-expandable, bioresorbable, vascular stentelements configured to be implanted in the blood vessel as amulti-element stent, with the multiple stent elements not touching oneanother; wherein the stent elements comprise an alternating sequence oftwo larger cells and a set of smaller cells; wherein the two largercells are formed by a pivoting strut between the two larger cells. 15.The device of claim 14, wherein the pivoting strut is configured topivot from a less rigid state to a more rigid state.
 16. A method ofmaking a multi-element, bioresorbable, vascular stent, the methodcomprising: forming a length of the bioresorbable, vascular stent from abioresorbable material that is balloon expandable and not self-expandingusing an additive manufacturing process, wherein the stent elementscomprise a first set of closed cells and a second set of closed cellshaving a different shape or size than the first set of closed cells,wherein the first set of closed cells have a repeating longitudinallyaligned pattern and a repeating circumferentially aligned pattern,wherein the second set of closed cells have a repeating longitudinallyaligned pattern and a repeating circumferentially aligned pattern,wherein the first set of closed cells and the second set of closed cellsare circumferentially offset, and wherein the first set of closed cellsand the second set of closed cells have a helically aligned alternatingpattern; and cutting the length of the bioresorbable, vascular stent toform multiple stent elements of the stent; wherein the first set ofclosed cells and the second set of closed cells are formed using theadditive manufacturing process.
 17. The method of claim 16, wherein theadditive manufacturing process comprises micro-stereolithography. 18.The method of claim 16, wherein the additive manufacturing processcomprises 3D printing.
 19. The method of claim 16, wherein thebioresorbable material is selected from the group consisting ofpoly(L-lactic acid) (PLLA), polyglycolic acid (PGA), and poly(iodinateddesaminotyrosyl-tyrosine ethyl ester) carbonate.
 20. The method of claim19, further comprising applying a coating to the bioresorbable material.21. The method of claim 20, wherein the coating comprisespoly-D,L-lactide (PDLLA).
 22. The method of claim 16, further comprisingapplying a drug to the stent.
 23. The method of claim 22, wherein thedrug is selected from the group consisting of everolimus and otheranti-proliferative drugs.
 24. A method for maintaining or enhancingblood flow through a blood vessel, the method comprising: advancing aballoon catheter into the blood vessel; expanding a balloon on theballoon catheter to expand multiple, bioresorbable, vascular stentelements disposed on the balloon to contact an inner wall of the bloodvessel, wherein the stent elements comprise a first set of closed cellsand a second set of closed cells having a different shape or size thanthe first set of closed cells, wherein the first set of closed cellshave a repeating longitudinally aligned pattern and a repeatingcircumferentially aligned pattern, wherein the second set of closedcells have a repeating longitudinally aligned pattern and a repeatingcircumferentially aligned pattern, wherein the first set of closed cellsand the second set of closed cells are circumferentially offset, andwherein the first set of closed cells and the second set of closed cellshave a helically aligned alternating pattern; deflating the balloon,while leaving the vascular stent elements in place in the blood vessel;and removing the balloon catheter from the blood vessel.
 25. The methodof claim 24, wherein the blood vessel comprises a peripheral bloodvessel.
 26. The method of claim 24, wherein expanding the stent elementscomprises expanding at least four stent elements.
 27. The method ofclaim 24, wherein the stent elements are separated from one anotheralong the balloon, and wherein expanding the stent elements comprisesdelivering the stent elements to the inner wall of the blood vessel in aspaced-apart configuration.